How To Read A Perpetual Calendar Before You Buy One

A perpetual calendar tracks the length of every month and the four-year leap cycle, which means the mechanism carries a memory of forty-eight months. Left running, it will not need correcting for the better part of a century.

Left stopped, it becomes a liability. Restarting one out of sequence, or forcing a correction through a date change window, is how service bills reach five figures.

For a buyer, the dial matters more than the calendar. Aperture spacing, font weight, the exact tail of a numeral, the finish of the moon disc. These change across production periods, and the market prices originality above everything else on complicated references.

Ask when it was last serviced, who by, and whether the dial has ever been off the movement. Then ask to see it running for a week before you commit.

The complication will outlive everybody in the transaction. The paperwork is the fragile part.